Edit File: _sha.py
# -*- coding: iso-8859-1 -*- """A sample implementation of SHA-1 in pure Python. Framework adapted from Dinu Gherman's MD5 implementation by J. Hallén and L. Creighton. SHA-1 implementation based directly on the text of the NIST standard FIPS PUB 180-1. """ __date__ = '2004-11-17' __version__ = 0.91 # Modernised by J. Hallén and L. Creighton for Pypy import struct, copy # ====================================================================== # Bit-Manipulation helpers # # _long2bytes() was contributed by Barry Warsaw # and is reused here with tiny modifications. # ====================================================================== def _long2bytesBigEndian(n, blocksize=0): """Convert a long integer to a byte string. If optional blocksize is given and greater than zero, pad the front of the byte string with binary zeros so that the length is a multiple of blocksize. """ # After much testing, this algorithm was deemed to be the fastest. s = '' pack = struct.pack while n > 0: s = pack('>I', n & 0xffffffff) + s n = n >> 32 # Strip off leading zeros. for i in range(len(s)): if s[i] != '\000': break else: # Only happens when n == 0. s = '\000' i = 0 s = s[i:] # Add back some pad bytes. This could be done more efficiently # w.r.t. the de-padding being done above, but sigh... if blocksize > 0 and len(s) % blocksize: s = (blocksize - len(s) % blocksize) * '\000' + s return s def _bytelist2longBigEndian(list): "Transform a list of characters into a list of longs." imax = len(list) // 4 hl = [0] * imax j = 0 i = 0 while i < imax: b0 = ord(list[j]) << 24 b1 = ord(list[j+1]) << 16 b2 = ord(list[j+2]) << 8 b3 = ord(list[j+3]) hl[i] = b0 | b1 | b2 | b3 i = i+1 j = j+4 return hl def _rotateLeft(x, n): "Rotate x (32 bit) left n bits circularly." return (x << n) | (x >> (32-n)) # ====================================================================== # The SHA transformation functions # # ====================================================================== def f0_19(B, C, D): return (B & C) | ((~ B) & D) def f20_39(B, C, D): return B ^ C ^ D def f40_59(B, C, D): return (B & C) | (B & D) | (C & D) def f60_79(B, C, D): return B ^ C ^ D f = [f0_19, f20_39, f40_59, f60_79] # Constants to be used K = [ 0x5A827999, # ( 0 <= t <= 19) 0x6ED9EBA1, # (20 <= t <= 39) 0x8F1BBCDC, # (40 <= t <= 59) 0xCA62C1D6 # (60 <= t <= 79) ] class sha: "An implementation of the MD5 hash function in pure Python." digest_size = digestsize = 20 block_size = 1 def __init__(self): "Initialisation." # Initial message length in bits(!). self.length = 0 self.count = [0, 0] # Initial empty message as a sequence of bytes (8 bit characters). self.input = [] # Call a separate init function, that can be used repeatedly # to start from scratch on the same object. self.init() def init(self): "Initialize the message-digest and set all fields to zero." self.length = 0 self.input = [] # Initial 160 bit message digest (5 times 32 bit). self.H0 = 0x67452301 self.H1 = 0xEFCDAB89 self.H2 = 0x98BADCFE self.H3 = 0x10325476 self.H4 = 0xC3D2E1F0 def _transform(self, W): for t in range(16, 80): W.append(_rotateLeft( W[t-3] ^ W[t-8] ^ W[t-14] ^ W[t-16], 1) & 0xffffffff) A = self.H0 B = self.H1 C = self.H2 D = self.H3 E = self.H4 """ This loop was unrolled to gain about 10% in speed for t in range(0, 80): TEMP = _rotateLeft(A, 5) + f[t/20] + E + W[t] + K[t/20] E = D D = C C = _rotateLeft(B, 30) & 0xffffffff B = A A = TEMP & 0xffffffff """ for t in range(0, 20): TEMP = _rotateLeft(A, 5) + ((B & C) | ((~ B) & D)) + E + W[t] + K[0] E = D D = C C = _rotateLeft(B, 30) & 0xffffffff B = A A = TEMP & 0xffffffff for t in range(20, 40): TEMP = _rotateLeft(A, 5) + (B ^ C ^ D) + E + W[t] + K[1] E = D D = C C = _rotateLeft(B, 30) & 0xffffffff B = A A = TEMP & 0xffffffff for t in range(40, 60): TEMP = _rotateLeft(A, 5) + ((B & C) | (B & D) | (C & D)) + E + W[t] + K[2] E = D D = C C = _rotateLeft(B, 30) & 0xffffffff B = A A = TEMP & 0xffffffff for t in range(60, 80): TEMP = _rotateLeft(A, 5) + (B ^ C ^ D) + E + W[t] + K[3] E = D D = C C = _rotateLeft(B, 30) & 0xffffffff B = A A = TEMP & 0xffffffff self.H0 = (self.H0 + A) & 0xffffffff self.H1 = (self.H1 + B) & 0xffffffff self.H2 = (self.H2 + C) & 0xffffffff self.H3 = (self.H3 + D) & 0xffffffff self.H4 = (self.H4 + E) & 0xffffffff # Down from here all methods follow the Python Standard Library # API of the sha module. def update(self, inBuf): """Add to the current message. Update the md5 object with the string arg. Repeated calls are equivalent to a single call with the concatenation of all the arguments, i.e. m.update(a); m.update(b) is equivalent to m.update(a+b). The hash is immediately calculated for all full blocks. The final calculation is made in digest(). It will calculate 1-2 blocks, depending on how much padding we have to add. This allows us to keep an intermediate value for the hash, so that we only need to make minimal recalculation if we call update() to add more data to the hashed string. """ leninBuf = len(inBuf) # Compute number of bytes mod 64. index = (self.count[1] >> 3) & 0x3F # Update number of bits. self.count[1] = self.count[1] + (leninBuf << 3) if self.count[1] < (leninBuf << 3): self.count[0] = self.count[0] + 1 self.count[0] = self.count[0] + (leninBuf >> 29) partLen = 64 - index if leninBuf >= partLen: self.input[index:] = list(inBuf[:partLen]) self._transform(_bytelist2longBigEndian(self.input)) i = partLen while i + 63 < leninBuf: self._transform(_bytelist2longBigEndian(list(inBuf[i:i+64]))) i = i + 64 else: self.input = list(inBuf[i:leninBuf]) else: i = 0 self.input = self.input + list(inBuf) def digest(self): """Terminate the message-digest computation and return digest. Return the digest of the strings passed to the update() method so far. This is a 16-byte string which may contain non-ASCII characters, including null bytes. """ H0 = self.H0 H1 = self.H1 H2 = self.H2 H3 = self.H3 H4 = self.H4 input = [] + self.input count = [] + self.count index = (self.count[1] >> 3) & 0x3f if index < 56: padLen = 56 - index else: padLen = 120 - index padding = ['\200'] + ['\000'] * 63 self.update(padding[:padLen]) # Append length (before padding). bits = _bytelist2longBigEndian(self.input[:56]) + count self._transform(bits) # Store state in digest. digest = _long2bytesBigEndian(self.H0, 4) + \ _long2bytesBigEndian(self.H1, 4) + \ _long2bytesBigEndian(self.H2, 4) + \ _long2bytesBigEndian(self.H3, 4) + \ _long2bytesBigEndian(self.H4, 4) self.H0 = H0 self.H1 = H1 self.H2 = H2 self.H3 = H3 self.H4 = H4 self.input = input self.count = count return digest def hexdigest(self): """Terminate and return digest in HEX form. Like digest() except the digest is returned as a string of length 32, containing only hexadecimal digits. This may be used to exchange the value safely in email or other non- binary environments. """ return ''.join(['%02x' % ord(c) for c in self.digest()]) def copy(self): """Return a clone object. Return a copy ('clone') of the md5 object. This can be used to efficiently compute the digests of strings that share a common initial substring. """ return copy.deepcopy(self) # ====================================================================== # Mimic Python top-level functions from standard library API # for consistency with the _sha module of the standard library. # ====================================================================== # These are mandatory variables in the module. They have constant values # in the SHA standard. digest_size = 20 digestsize = 20 blocksize = 1 def new(arg=None): """Return a new sha crypto object. If arg is present, the method call update(arg) is made. """ crypto = sha() if arg: crypto.update(arg) return crypto if __name__ == "__main__": a_str = "just a test string" assert 'da39a3ee5e6b4b0d3255bfef95601890afd80709' == new().hexdigest() assert '3f0cf2e3d9e5903e839417dfc47fed6bfa6457f6' == new(a_str).hexdigest() assert '0852b254078fe3772568a4aba37b917f3d4066ba' == new(a_str*7).hexdigest() s = new(a_str) s.update(a_str) assert '8862c1b50967f39d3db6bdc2877d9ccebd3102e5' == s.hexdigest()